The invention relates to a railway track tamping machine, especially a track levelling and aligning machine which is equipped with at least one ballast tamping unit which is longitudinally movably mounted on the machine frame and has at least one pair of co-operating tampers which are vertically adjustable.
Track tamping machines which proceed with a uniform velocity and on which intermittently working longitudinally movable tamping units are mounted are already known, see German published application No. 1,067,837 and U.S. Pat. No. 3,455,249. These machines are different from conventional track tamping machines which move in steps from tie to tie and, therefore, need to be accelerated very quickly as well as decelerated very quickly. Machines of which the frame is uniformly moved and on which only the tamping units have to move periodically, have the advantage that the masses to be accelerated and to be decelerated at each tamping cycle are considerably smaller than the step moving machines and the necessary energy and forces to move these masses are consequently smaller. Known uniform movement track tamping machines have tamping units longitudinally movable along the machine frame. Such arrangements are afflicted with adjustment problems. After completing the tamping of one tie and having lifted the tamping tools above the level of the rails, the tamping units have to be moved from the rear end position of the track travel on the machine chassis quickly into the front end position on the machine frame and be lowered into the track. During the succeeding tamping cycle the tamping units must be moved relative to the frame backwardly at a speed appropriate to the forward speed of the machine frame. The control of such relative movement and the adjustment of the tamping unit into the correct working position presents difficulties, particularly if the tamping unit is suspended in guides for sliding movement on the machine frame.
The same disadvantages are found in principle with another known track tamping, levelling and aligning machine see Austrian Patent No. 350,612 which comprises a main frame and an additional frame which is coupled to the main frame by a longitudinal moving device so that part of the machine can be moved with uniform speed and another part of the machine can be moved in step-wise sequence.
The present invention seeks to simplify the machine as well as the control of the workheads.